Method of and apparatus for controlling alternating current



July 14, 1931. D. G. MOCAA 1,814,051

METHOD OF AND APPARATUS FOR CONTROLLING ALTERNATING CURRENT Original Filed Dec. 8, 1925 2 Sheets-Sheet 1 A TTOR/YEV July 14, 1931. D. G. McCAA 1,814,051

METHOD OF AND APPARATUS FOR CONTROLLING ALTERNATING CURRENT Original Filed Dec. 8, 1925 2 Sheets-Sheet 2 [N VEIVTO/P Patented July 14, 1931 UNIT ED ST A T E S PATENT OFFICE DAVID G. MCCAA, F PHILADELPHIA, PENNSYLVANIA Application filed December 8, 1925, Serial lily invention relates to a method of and apparatus for controlling fluctuating unidirectional current or alternating current, and relates more particularly to a method of 5 and apparatus for di fierentiating between fluctuating or alternating currents of difierent amplitudes or electro-motive-forces of the same or. different frequencies.

In accordance with my invention the alter- IO hating or fluctuating currents or electroniotiveforces are su'b'ected to a uni-directional electro-motive-i orce or". substantially constant magnitude and substantially equal to theelectro-motive--force of smaller amplitude, and the currents or electro-motivees so modified are so applied to a translating device that effect thereon of the current or electro-mot-ive-force of larger amplitude is'materially reduced or the eii'ect of the current or electro-motive-force of smaller amplitude upon the translating device is nniterially relatively increased.

My lIT'QHtiOH resides in a method and r paratus oi the character hereinafter de 'bed and-claimed.

For an understanding of my method and for an illustration of the various forms my apparatus may take, reference is to be had to the accompanying-drawings in which F 1 is a diagram of a radio receiving un in which the currents of different amplitudes as modified by uni-directional electro-motive-force of-substantially constant magnitude control relays which in turn cont-rel the impression upon. the signal translang instrument of currents. of substantially equal amplitudes representative of the cur rents of different amplitudes.

Fig. lais a diagram of a modification. Fig. a diagram of a radio receiving sy tem in which currents of different amplitu as as modified by uni-directional electromotiveforce of substantially constant magnitude-control to substantially equal extents an electromagnetic system.

Fig. 3 is a diagram of a modification.

Figs. l, 5 and 6 are explanatory graphs.

In Fig. 1' there are indicated two asymmetric conductors as thermionic vacuum tubes V and V1v each comprising an anode a No. 74,087. Renewed November 6, 1930.

and hot filament or cathode F. .rissociated with these tubes are the magnetic field coils M "d Mlv which when traversed by current Vii .s, as well understood in the art, the impedance between the anodes and cathodes of the tubes. The coils are connected in parallel branches to one terminal of the source S, again representing a source of audio frequency currents of differentamplitudes and of diii'er nt characteristics, the lesser amplitude gc, r lly again representing the desired signal or message. In circuit with the tubes V, V1 are the primaries 29, p1 and the source of current B, the primaries p, 221 opposing e ch other in their effect upon the secondary to which is connected the instrument T.

As thus tar described, the currents of both low and high amplitude are balanced out and have no effect upon the instrument T. This may be understood upon reference to Fig. 4 in which the curve m represents an alternating current through the coil M and the curve ml represents the alternating current simultaneously existing in the coil M1. The curve 79 shows the variation of current from the source B in the primary p for the current at in the coil M; and similarly the curve pl represents the current from the source B through the prinmary p1 for the current ml in the coil M1. As is apparent, the current impulses p and 721 are in phase and neutralize each other.

The system. of Fig. 1 is rendered suitable for differentiating between the low and high amplitude currents from the sources S by recourse to the sources of electro-motiveforce E and E1 connected in opposite senses with respect to the source S in the circuits of the coils M and M1 respectively.

As indicated in the right-hand portion of Fig. 4, there is shown a curve m2 which is the resultant of the curve m and electro-moti'veforce E. The sources E in effect shifts the curve m upwardly so that it varies periodically between positive maxima and zero. Similarly the curve m3 shows the efiect of the electro-motiveforce E1 upon the current m1, shifting it entirely below the Zero Whereby the current through the coil Ml varies from zero through successive negative maxima. The result upon the current through the primary 1) is indicated by the curve 102 and the effect upon the current through the primary p1 is indicated by the curve p8. The curves p2 and 103 show that the currents through the primaries p and p1 representative of the low amplitude current representing the signal now are in effect dephased 180 degrees with respect to each other and, therefore, act cumulatively upon the secondary S, and accordingly the desired low amplitude signal-representing current afiects the instrument T, while the large amplitude current only slightly affects instrument T.

In Fig. 1a a similar arrangement is applied to the radio frequency currents, both those of low amplitude representing the desired signal and those of greater amplitude representing oscillations due to static or other interference. In this case'the secondary Sr is such a source of radio frequency currents of different amplitudes and characteristics. The sources E and E1 are connected in parallel branches between one terminal of the source S1 and the coils M, M1 associated with tubes V, V1. The circuit of the secondary Sr may be provided with the tuning condenser C. In this instance the tubes V and V1 are connected in circuit respectively with radio frequency transformer primaries p and p1. opposite y affecting the secondary 8 whose circuit is tunable to the radio frequency by the condenser C1. Such radio frequency current as reaches the secondary circuit 8 is impressed upon the detector tube D which either directly, or through suitable audio frequency amplifiers, controls the signal translating instrument or telephone T.

Here again by the low amplitude signalrepresenting current the secondary is affected, with resultant effect upon the instrument T, while the interfering radio frequency current of high amplitude is but little affected by the small electro-motive-forces E and E1 and there is, therefore, a substantial balancing out of the current of large amplitude.

To concentrate the magnetic flux in the region or path of the electron stream between anode and cathode in tubes such as V, V1 of Figs. 1 and 1a Where the impedance is controlled by a magnetic field produced by the windings M and M1, it is desirable to construct the anode a of magnetizable material as iron, nickle, etc., with the result that a greater impedance variation is procured for a given magneto-motive-force produced by the coil M or M1. Or between anode and cathode may be disposed a grating, open work gauge or the like of iron or other magnetizable material for the same purposes, and

preferably insultated from both anode and cathode.

In Fig. 2, S is again a source of audio frequency currents of different amplitudes and characteristics. The magnet windings M and M1 are connected in parallel branches with the source S and in series with the coils are sources of electro-motive-force E and E1. The coils M, M1 in this case are disposed upon soft iron cores 0 and c1 of a magnetic circuit comprising them and the soft iron yoke y. Disposed between the poles of the cores 0 01 is a soft iron armature or reed R, pivoted or secured at its end 6 to the yoke y. The reed or armature R mechanically actuates any suitable means, as, for example, a diaphragm o as through the intervening vibration transmitting member g. The diaphragm 0 may be that of a microphone or an instrument for directly reproducing sound. The action is in general similar to that described in connection with Fig. 1 in that the coils M, M1 are wound in such directions or so connected that they oppose each other in their effect upon the armature or reed R.

. As indicated in Fig. 5 the curve m represents an audio frequency current of low amplitude representing the desired signal and is that flowing through the coil M. Similarly, the curve m1 represents the current simultaneously flowing through the coil M1. The arrows indicate the directions of the forces simultaneously acting upon armature or reed R when the sources E and E1 are absent. By

introduction of these electro-motive-forces I E and E1, however, the curve m is shifted, as indicated in the right-hand portion of Fig.

5, to the position m9. and the curve m1 is shifted tothe position m3, m2 indicating that the current is now all uni-directional and varies between zero and successive positive maxima, while the current m3 is again entirely uni-directional and varies between zero and successive negative maXim'a. The arrows indicate that the forces now exerted by the signal-representing current of low amplitude upon the reed or armature R are in effect dephased from the left-hand portion of Fig. 5, as when the sources E and E1 are absent. The result is that with the electro-motiveforces E and E1 present and substantially equal in amplitude to the amplitude of the signal-representing current the coils M and M1 operate cumulatively upon the armature or reed R, causing it to operate a microphone, diaphragm or any other device or instrument. Simultaneously, however, the interfering current of large amplitude has but slight effect upon the reed or armature B. As indicated in Fig. 6, the halves of the interfering current of large amplitude are represented by the curves m4 and m5 passing respectively through the coils M and M1. The feeble electro-motive-force E assists the current m4 slightly, yielding a current represented by the curve m6, while simultaneously the electromotive-force E1 slightly opposes the current represented by the curve m5, yielding a current represented by the curve m7. As indicated by the arrows in Fig. 6,there is, therefore, but a slight difference in the forces exerted upon the reed or armature R by the magnet M, M1 as regards the large amplitude current.

The sources of electro-motiveforce E and E]. may be omitted in Fig. 2 and in lieu of them may be utilized adjustable permanent magnets acting respectively upon the cores and 01 to alter the net field intensities to correspond in general with the graphs indicated in Figs. 5 and 6 regarding currents.

In Fig. 3 the system comprises permanently magnetized elements for causing the soft iron of the magnetic system to operate at suitable portions of its magnetization curve. In this instance the coils M and M1 are disposed upon soft iron cores 0 and 01 carried by soft iron yokes y at whose opposite ends are the cores c2 and 03 upon which are disposed the coils M2 and M3. Midway of the yokes are disposed the permanent bar magnets I and I1 whose neighboring poles are of like signs. The armature or reed R in this case is pivoted at its center adjacent the neighboring poles of the permanent magnets, while its free ends are disposed in the spaces between the opposite pairs of the cores. As before stated, the armature R operates a microphone, diaphragm or any other suitable means through the mechanical connection The magnet windings M, Mlare connected in parallel branches of the secondary S which is again a source of audio frequency currents of different amplitudes and characteristics, the current of lesser amplitude representing the desired signal or message. In circuit with the coils M and M1 are again the sources of electro-motiveforce E and E1 respectively.

The coils M2, M3 are connected in parallel with each other and the secondary source S1 of similar audio frequency currents of different characteristics and amplitudes.

First assuming the sources of E, E1 absent, the system is balanced in the sense that no force is exerted upon the armature B because the coils M and M2 operate cumulatively during one half wave with each other and the permanent magnet I to increase the magnetic flux through the cores 0 and 02 which causes 1"; application to opposite ends of the armature R of equal forces with zero resultant upon the armature R. During the same half wave the coils M1 and M3 operate cumulatively with each other but in opposition to the permanent magnet 11 to decrease the magnetic flux through the cores c1 and 03, these cores (:1 c3 exerting equal and opposite forces, if any, upon the armature R, again effecting balance. During the next half cycle or half wave the situation is reversed in that the poles c1 and 03 now exert strong forces upon armature R to effect balance, while the cores (2 and c2 exert small forces, if any, which balance each other upon the armature R.

In consequence the currents of both small and great amplitudes have no effect upon the armature R.

With the electro-motive-forces E and E present, however, the following action takes place. The electro-motive-force E acts to decrease the magnetic flux produced in the coil M for the positive peak of the low ampliture currents by a greater amount than the decrease in the magneto-motive-force in coil M thereby causing coil M to pull the armature R against the force of the coil M. The electro-motive-force E at the same time adds to the magnetic flux produced by the signal in coil M so that the total magnetic flux of coil M is greater than that of M by the amount of the electro-motiveforce E thereby causing the coil M to attract the other end of the armature R against the magnetomotive-force of the coil M There is, therefore, a couple produced on the armature R with coil M pulling the armature R in one direction around its center and coil M pulling with an equal force in the opposite direction around the same center, thereby producing a response on the microphone O by means of the member Q. The currents of higher amplitude, however, are so much greater than the electro-motive-forces E and E that they are affected only to a very small extent thereby and their amplitudes are increased and decreased only slightly so that their components are substantially balanced as shown in F i 6 and produce a very little or substantia ly no effect on the microphone O.

,VVhat I claim is:

1. The method of differentiating between fluctuating or alternating currents of different amplitudes which comprises dividing said currents into components, causing said components of both currents to oppose each other in their effect upon a translating device, and opposing one of the components of the current of lesser amplitude by a constant uni-directional electro-motive-force of magnitude comparable with the magnitude of said component of said current of lesser amplitude to cause the other component of said current of lesser amplitude to affect said translating device.

2. The method of producing a mechanical effect by one of several currents of different amplitudes, which comprises dividing the currents into components, producing magneto-motive-forces opposing each other in their effect upon a pivotal member, and causing an unbalance of the effect of the magnetomotive-forces upon said pivotal member with respect to the current of lesser amplitude by opposing to a component of the current of lesser amplitude a uni-directional electromotive-force of magnitude comparable to the magnitude of said component.

3. The method of producing a mechanical effect by one of several currents of different amplitudes, which comprises dividing the currents into components, producing magneto-motive-forces opposing each other in their effect upon a pivotal member, and causing an unbalance of the effect of the magnetomotive-forces upon said pivotal member with respectto the current of lesser amplitude by opposing to a component of the current of lesser amplitude a uni-directional electromotive-force of magnitude comparable to the magnitude of said component, and adding to the other component of the current of lesser amplitude a uni-directional electro-motiveforce.

4. The combination with a source of fluc- 1 tuating or alternating currents of different amplitudes, a translating device, means comprising separate circuits for dividing said currents into components, means causing said components to substantially balance each other in their efiect upon said translating device, and a source of uni-directional electromotive-force in one of said circuits and of magnitude comparable With the magnitude of the component of said current of lesser amplitude in that circuit to cause the other component of said current of lesser amplitude to affect said translating device.

5. In a receiving system in which occur audio frequency currents of different amplitudes representing, respectively, the desired signal and interfering energy, the combination with means comprising separate circuits for dividing said currents into components, of a signal translating instrument,means causing 2 said components to oppose each other in their effect upon-said instrument, and a source of uni-directional electro-motive-force in one of said circuits and of magnitude comparable to the magnitude of said component of said current of lesser amplitude in that circuit to oppose at least one of said components of said current of lesser magnitude.

' 6. In radio reception, the method of difl'erentiating between radio frequency currents of different amplitudes and representing respectively the desired signal and interfering energy, which comprises dividing said currents into components, causing said components of both currents to oppose each other in their eifect upon a single-translating instrurents of different amplitudes representing respectively the desired signal and an interfering effect, dividing said currents into components, causing said'components to oppose each other in their effect upon a signal-translating instrument, passing said components simultaneously through asymmetric conductors, and opposing to the component of the current of lesser amplitude passed through one of said asymmetric conductors a uni-directional electro-motive force of magnitude comparable to the magnitude of said component of the current of lesser amplitude to cause an effect upon said signal-translating instrument.

8. 11 radio reception, the method which comprises producing audio frequency currents of different amplitudes representing respectively the desired signal and an interfering effect, dividing said currents into components, causing said components to oppose each other in their effect upon a signal-translating instrument, passing said components simultaneously through asymmetric conductors, opposing to the component of the current of lesser magnitude passed through one of said asymmetric conductors a uni-directional electro-motive force of magnitude comparable to the magnitude of said com ponent of the current of lesser amplitude to cause an effect upon said signal-translating instrument, and adding to the other component of said current of lesser magnitude passed through the other asymmetric conductor a uni-directional electro-motive force of magnitude comparable to the magnitude of said component of-said current of lesser amplitude to increase the effect upon said signal-translating instrument.

9. In radio reception, the method of differentiating between radio frequency currents of different amplitudes and represent ing, respectively, the desired signal and interfering energy, which comprises producing audio frequency currents representing the radio frequency currents of different amplitudes, dividing the audio frequency currents into components, causing the components of the audio frequency currents representing the desired signal and interfering energy to oppose each other in their effect upon a signal translating instrument, and subjecting at least one of said components of lesser amplitude to a uni-directional electro-motive force of a magnitude comparable to the magnitude of said current of lesser amplitude to cause an effect upon said signal-translating instrument.

DAVID G. MoOAA. 

